Timing switch with means for urging a pair of contact arms into pressure engagement with a pivotal shaft and rotatable cam



June 2, 1970 c.cHuRcH ETAL 3,515,831

' TIMINGSWITCH WITH MEANS FOR URGING A PAIR OF CONTACT ARMS INTO PRESSURE ENGAGEMENT WITH A PIVOTAL SHAFT AND ROTATABLE CAM med .June 1, 196e I 38 gg U.S. Cl. 200-153 United States Patent Office Patented June 2, 1970 l 3,515,831 TIMING SWITCH WITH MEANS FOR URGING A PAIR OF CONTACT ARMS INTO PRESSURE ENGAGEMENT WITH A PIVOTAL SHAFI` AND ROTATABLE CAM Charles Church, Whitewater, Wis., Henry J. Flajole,

Menominee, Mich., and Harold Kerber, Janesville, Wis., assignors to The Bunker-Ramo Corporation, a corporation of Delaware Filed June 1, 1966, Ser. No. 554,517 The portion of the term of the patent subsequent to Nov. 17, 1985, has been disclaimed Int. Cl. H01h 19/62 9 Claims ABSTRACT OF THE DISCLOSURE A cam-operated mechanical switching device employing only a single cam but capable of generating a short, accurately timed electrical pulse by a mechanism which is relatively insensitive to vibration and which is adapted to mass production manufacture without requiring manual adjustment. The contacts for the switching device are attached to a pair of contact arms, -which overlie each other, and

are mounted on the same shaft. Cam follower means are on the ends opposite the shaft of the contact arms.

This invention relates to switching devices and more particularly to mechanical switching devices for providing a timing pulse. i

Mechanical switches are widely used in industry to provide timing signals for the operation of clocks, valves and relays. As an example thereof, a mechanical switch is used to provide an output timing pulse from a master sender timer, which output pulse is used to control the time of slave clocks remote from the master sender. The master sender generally comprises a conventional timepiece movement which, through cam means, actuates a mechanical switching device to periodically generate an output pulse (usually one pulse per minute). The slave clock generally comprises a stepping motor electrically connected to the mechanical switch of the master sender timer. The shaft of the stepping motor angularly rotates a predetermined amount for each input pulse received. The angular rotation of the motor shaft is translated through a gear train to the minute and hour hands of the clock face to indicate time.

In general, the prior art construction for a mechanical switch as used supra is as follows. A pair of cams are connected to and driven by a conventional timepiece movement. Two contact arms of a flexible spring material are xedly mounted at one end thereof and a pair of contacts are each mounted in line on an associated one of said arms at the other end thereof so that they are normally open but engageable with respect to each other. The contact arms are bent so that they each pressure engage the periphery of an associated cam. The cams each have a drop-off from one level thereof and are keyed together on a common shaft from the timepiece movement so that as they turn the free end of one contact arm falls on the drop-off of its cam before the other contact ann falls on the drop-off of its cam. This premature falling by one contact arm closes the contacts to produce an output pulse. Further rotation of the cam assembly permits the other contact arm to fall on its drop-off thereby opening the contacts to their normal condition. The length of time that the contacts stay together is determined bythe difference in time between drop-off of the contact arms from the aforementioned cams. The two cams must therefore be accurately aligned to each other and small variations between the cams causes timing variations. Using this construction, it is generally necessary that the timing be calibrated by hand bending the contact arms to change the length in engagement with the cams and thereby change the drop-off time of occurrence therefor. This type of switch is unsatisfactory. It has a large timing error, approximately plus or minus one-half second. The thin cross section of the contact arms, necessary to permit adjustment of the length thereof, makes the switch vibration sensitive resulting on occasion in false contact engagement. Further, it is not generally suited to production manufacturing techniques.

It is, therefore, one object of the present invention to provide an improved switching device for providing a timing pulse.

It is another object of the present invention to provide a mechanical switching device capable of generating an accurate timing pulse.

It is another object of the present invention to provide a mechanical switching device which is relatively insensitive to vibration and which is capable of generating a timing pulse.

Other objects of the present invention will become more apparent as the detailed description proceeds.

In general the present invention comprises a shaft and a pair of contact arms rotatably mounted at one end thereof on said shaft. One of the Contact arms is mounted to permit play between the contact arm and the shaft. A pair of contacts are each mounted to an associated contact arm at the other end thereof and spatially engageably disposed with respect to each other. Rotatable cam means are provided engageable with the contact mounted ends of said contact arms and having a drop-off from one level thereof. Means are provided for urging said contact arms into pressure engagement with the side of said shaft opposite the contact ends of said contact arms and for urging the contact ends of said contact arms into pressure engagement with said cam means. The drop-off of said cam means effects a change in the switching state of said contacts upon rotation of said cam means.

Further understanding of the present invention may best be obtained from consideration of the accompanying drawings wherein:

FIG. l is an elevational View of the preferred embodiment constructed according to the present invention.

FIG. 2 is a sectional view of the embodiment of FIG. 1 taken along lines 2 2.

FIGURE 3 is an exploded View of the preferred embodiment constructed according to the present invention.

In FIGS. l and 2 the device of the present invention is shown mounted on a plate assembly 10 through which a rotatable shaft 12 is passed. The shaft 12 is driven by a conventional timepiece movement, not shown. The shaft 12 is connected to and drives a cam 14 having a drop-off 16 from one level thereof.

A second shaft 18 is fxedly mounted to the contact plate 10. A rigid metal contact arm 20 is mounted at one end 22 thereof on shaft 18 so as to be rotatable with respect thereto. A plastic electrically insulating bushing 21 is fixedly mounted on the end 23 of shaft 18. A rigid metal contact arm 24 has one end 26 thereof rotatably mounted on plastic bushing 21 as shown. The opening in end 26 of contact arm 24 through which bushing 21 passes is sized larger than the bushing 21 to permit play between the arm 24 and bushing 21. A plastic member 28 is rotatably mounted on plastic bushing 21, interposed between ar-m 24 and arm 20. The opening in member 28 through which bushing 21 passes is sized larger than the diameter of the bushing 21 to permit play between member 28 and bushing 21. Contact arm 20 has a projection 30 having an aperture 31 therethrough to engage a pin 32 extending from member .28. Contact arm 24 has a projection 34 at the end 26 thereof which is engageable as shown with pin 36 extending from member 28.

A pair of contacts 38 and 40 are mounted respectively at the ends 42 and 44 of contact arms 20 and 24. The contacts 38 and 40 are mounted such that they are in line and spaced apart a predetermined distance when the end points 46 and 48 of Contact arms 20 and 24 respectively are engaged with cam 14. The end points 46 and 48 of contact arms 20 and 24 are equally spaced from the centers of the openings in ends 22 and 26 thereof about shaft 18 and bushing 21. Further, the end points 46 and 48 are spaced such that they ride on and engage the periphery of the cam 14 as shown.

A spring 54 is connected to the contact plate 10 and to a projection 56 of member 28. The spring 54 is under tension and positioned with respect to the axis between pins 32 and 36 so that a rotational force is applied to the member 28. The rotational force from spring 54 on member 28 causes member 28 to rotate about bushing 21 until pin 36 engages projection 34 of contact arm 24. The pressure engagement of pin 36 with projection 34 and the engagement of pin 32 with projection 30 imparts a pressure engagement to the end points 46 and 48 of contact arms 20 and 24 with the cam 14. Further the opening in the end 26 of contact arm 24 is brought in pressure engagement with the bushing 21 on the side 57 thereof opposite the cam 14, at the same time tending to shift arm 20 bodily to the left and arm 24 bodily to -the right. This action, with the looseness provided between arm 24 and its pivot, causes a slight offset between the cam follower points 46 and 48. -Electrical connections are effected to the contacts by connections made to the contact arms 20 and 24.

In operation, as previously recited, the spring 54 urges the end points 46 and 48 of contact arms 20 and 24 into pressure engagement with the cam 14. Further the spring S4 urges the contact arm 24 into pressure engagement with bushing 21 about the side 57 thereof opposite the cam 14 whereby the end point 48 of contact arm 24 extends further than end point 46 of contact arm 20 in their engagement with cam 14. The rotation of the cam 14 is, as shown, in a clockwise direction thereby aiding rather than opposing pressure engagement of contact arm 24 with bushing 21. The contacts 38 and 40 are spaced apart a distance less than the drop-off 16 of cam 14. Thus, as the cam rotates in a clockwise direction, the end point 46 of contact arm 20 will encounter the dropoif 16 of cam 14 rst and contact 38 will engage contact 40. The engagement between contacts 38 and 40 will continue until the end point 48 of contact arm 24 encounters the drop-off 16 of cam 14, at which point the engagement between contacts 38 and `40 will be broken and the contacts will resume their normally open status for the remainder of the cam rotation cycle. The time of duration of closure of contacts 38 and 40 is dependent upon the relative distance between the end points 46 and 48 of contact arms 20 and 24 engaging cam 14, which distance is varied by enlarging or decreasing the diameter of the opening in the end 26 of arm 24.

It has been found that with the embodiment as aforedescribed, a timing switch may be constructed which is reliable, rugged and relatively insensitive to vibration. Further, such a switch is accurate to plus or minus onetenth of a second and does not require hand calibration after assembly. The switch is also readily adapted to production manufacturing.

Persons skilled in the art will, of course, readily adapt the teachings of the present invention to embodiments far different than the embodiment described above. Accordingly, the scope of protection afforded the present invention should be limited only in accordance with the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are dened as follows 1. A pulse generating electrical switching device comprising a pair of contact arms overlying each other and each having an opening therethrough, the centers of said openings being coaxial with each other and equispaced from a pair of cam-follower portions, each located at one end of one of said contact arms, pivotal shaft means mounted through said openings of said contact arms, said pivotal shaft means and one of said openings being sized to permit play therebetween, means for maintaining the sides of said openings opposite the ends of said contact arms equispaced of the centers thereof in pressure engagement with said pivotal shaft means, a pair of contacts engageable with each other and each mounted on an associated one of said contact arms, a single rotattable cam means pressure engaged with both of the camfollower portions at the ends of said contact arms equispaced of the centers of said openings and having a dropolf from one level thereof to effect a changed switching state between said contacts upon rotation of said cam means.

2. A switching device comprising shaft means, a pair of contact arms overlying each other with each of said arms pivotally mounted at one end thereof on said shaft means, at least one of said contact arms being mounted to permit play between said arm and said shaft means, a pair of contacts each mounted to an associated contact arm at the other end thereof and spatially engageably disposed with respect to each other, with a single rotatable cam means engageable with cam-follower portions adjacent the contact mounted ends of said contact arms and having a drop-oif from one level thereof, means for urging said contact arms into pressure engagement with the opposite sides of said shaft to cause the camfollower portions of said contact arms to assume positions offset from each other and for urging the contact ends of said contact arms into pressure engagement with said single cam means, the drop-off of said cam means effecting a two step successive change in the switching state of said contacts upon rotation of said single cam means. A

3. A switching device comprising first and second contact arms each having an opening therethrough, the centers of said openings being equispaced from a pair of cam-follower portions at one end of said contact arms, pivotal shaft means mounted through said openings of said contact arms, said pivotal shaft means and the opening of at least one contact arm being sized to permit play therebetween, means for ymaintaining the sides of said openings in the first and second contact arms in pressure engagement with opposite sides of said pivotal shaft means to cause the cam-follower portions to be oifset from each other to cause a sequential dropoif of said followers from one level thereof, with a first contact mounted on said first contact arm and a second contact mounted on said second contact arm a distance less than the drop-off of said cam means, whereby the sequential drop-off of said followers from the cam means will effect generation of a short timed electrical pulse through said contacts.

4. A switching device comprising first and second contact arms each having an opening therethrough at one end thereof, the centers of each of said openings being equispaced from the other end of said contact arms, a member having an opening therethrough, rotatable cam means engageable with the bottoms of said contact arms at the said other ends of said contact arms and having a drop-off from one level thereof, pivotal shaft means mounted through said openings of said contact arms and member, said pivotal shaft means and the openings of said member and said rst contact arm being sized to permit play therebetween, means for engaging said member with said rst and second contact arms to urge said bottoms of said contact arms in pressure engagement with said cam means while maintaining the sides of the openings of said contact arms opposite the said other ends thereof in pressure engagement with said pivotal shaft means, a contact mounted at the said other end of said rst contact arm, a contact mounted at the said other end of said second contact arm above said first arm contact a distance less than said drop-off of said cam means and engageable with said first arm contact, rotation of said cam means effecting a changed switching state of said contacts about the dropoff portion thereof.

5. The device according to claim 4 wherein said .member engaging means comprise a projection on said first contact arm at the end thereof having said opening, a first pin mounted on said member engageable with said first contact arm projection, a projection on said second contact arm at the end thereof having said opening, said second contact arm projection having an aperture therethrough, a second pin mounted on said member and sized to engage said second Contact arm projection aperture, and spring means mounted to said member to urge rotation thereof about said pivotal shaft means, said pins of said member urging Said Contact arms in pressure engagement with said cam means while maintaining the sides of the openings of said contact arms opposite the said other ends thereof in pressure engagement with said pivotal shaft means.

6. A switching device comprising shaft means, a pair of contact arms rotatably mounted at one end thereof on said shaft means, one of said contact arms being mounted to permit play between said arm and said shaft means, a pair of contacts each mounted to an associated contact arm at the other end thereof and spatially engageably disposed with respect to each other, rotatable cam means engageable with the contact mounted ends of said contact arms and having a drop-off from one level thereof, means rotatable about said shaft means engaging the mounted ends of said contact arms to urge said contact arms into pressure engagement with said cam means and pressure engagement with the side of said shaft means opposite the contact ends of said contact arms, and spring means mounted to said rotatable means to impart a rotational force to said rotatable means and effect said contact arm pressure engagements, said drop-off on said cam means effecting a change in the switching state of said contacts upon rotation of said cam means.

7. The device according to claim 6 wherein said contacts are spatially separated a distance less than the dropoff of said cam means; said rotatable means comprise a member interposed of said contact arms rotatably on said shaft means to permit play between said shaft means and said member, a projection on each of said contact arms at the end thereof mounted on said shaft means, a pair of pins mounted on opposing sides of said member each engageable with an associated one of said projections to urge said contact arms in pressure engagement with said shaft means on the side thereof opposite the contact ends of said contact arms and with said cam means; said spring means are mounted to said member to impart a rotational force thereto; and said cam means rotate in the same direction as the rotational force applied to said member.

8. A switching device comprising a mounting plate,

a driven first shaft extending through said plate, a cam having a drop-off from one level thereof mounted on said first shaft to rotate therewith, first and second rigid metal contact arms each having an opening therethrough at one end thereof, a pivotal second shaft fixedly mounted to said mounting plate and extending through the opening in said second contact arm, a pivotal electrically insulating bushing fixedly mounted on said second shaft and extending through the opening of said first contact arm to permit play between said bushing and said lirst contact arm, the other ends of said contact arms being equispaced from the centers of said openings a distance to engage said cam, a contact mounted at said other end of said first contact arm, a contact mounted at said other end of said second contact arm above said first arm contact a distance less than the drop-off of said cam and engageable with said first arm contact, and means for urging said first contact arm in pressure engagement with said bushing about the side thereof opposite said other ends of said contact arms while urging said other ends of said contact arms in pressure engagement with said cam, the drop-off of said cam effecting a changed switching state of said contacts upon rotation of said cam.

9. The device according to claim 8 wherein said urging means comprise an electrically insulating member interposed of said contact arms rotatably about said bushing to permit play between said bushing and said member, a projection on said first contact arm at the end thereof having said opening, a first pin mounted on said member engageable with said first contact arm projection, a projection on said second contact arm at the end thereof having said opening, said second contact arm projection having an aperture therethrough, a second pin mounted on said member and sized to engage the aperture of said second contact arm projection, a spring tension mounted to said mounted plate and said member to impart rotational force to said member about said bushing, said pins of said member urging said other ends of said contact arms in pressure engagement with said cam while urging said first contact arm in pressure engagement with said bushing about the side thereof opposite said other ends of said contact arms, and said cam rotates in the same direction as the rotational force imparted to said member about said bushing.

References Cited UNITED STATES PATENTS 8/1962 Manning 200-30 FOREIGN PATENTS 8/ 1960 Australia. 5 1963 Canada. 7/ 195 8l Germany.

ROBERT K. SCHAEFER, Primary Examiner R. A. VANDERHYE, Assistant Examiner U.S. Cl. X.R. 

